Chewing gum consists of two major portions, masticatory and non-masticatory. The masticatory portion is usually called chewing gum base, and often includes filler, while the non-masticatory portion consists mostly of sweetening and flavoring ingredients.
For a long time, natural water-insoluble gums of vegetable origin, i.e., chicle, were used for the major portion of chewing gum base. Unfortunately, the natural gums are subject to substantial price fluctuations as well as unpredictability of supply. Because of these reasons, manufacturers have in recent years tried with varying degrees of success to duplicate the desirable properties of natural gum by means of synthetic resins, rubber and other polymers.
U.S. Pat. No. 3,396,038 and patents referred to therein give representative showings of the art with respect to synthetic resin bases, particularly those of polyvinyl acetate derivation. The prior art also includes gum bases such as gluten (U.S. Pat. Nos. 2,586,675 and 1,700,387), prolamine (U.S. Pat. No. 3,469,861), and Zein (U.S. Pat. No. 2,489,147).
In U.S. Pat. No. 3,666,492 issued May 20, 1972 to Teng and Rha there is disclosed a fatty acid ester of starch as a chewing gum base. The invention of U.S. Pat. No. 3,666,492 involves a saturated fatty acid having from 8-14 carbon atoms (specifically starch laurate), and a degree of substitution of above 2.
In Ser. No. 450,052 there is disclosed a chewing gum base made from hydroxypropyl starch acetate having a degree of molecular substitution of hydroxypropyl radicals of about 3 to about 6 and a degree of substitution of acetyl groups of about 1.0 to about 2.5. Application Ser. No. 450,052 discloses the preparation of hydroxypropyl starch acetate from hydroxypropyl starch and acetic anhydride in toluene. The hydroxypropyl starch acetate is dissolved in the toluene, washed, and then hydroxypropyl starch acetate is precipitated from the toluene by adding hexane. The gum is purified by dissolving in chloroform, precipitating in hexane, and drying in a vacuum oven overnight.
The present invention described improved methods of making the gum base which is disclosed and claimed in Ser. No. 450,052. In the present process all reactants are maintained in either solution or emulsion form and this results in the following advantages over the process of Ser. No. 450,052:
1. The constituents of the entire process are conveniently handled as liquids rather than as sticky, elastic globs. That means the liquid can be efficiently stirred or easily transferred by pumping.
2. The uniformity of all reactions (hydroxypropylation, acetylation, and neutralization), is assured.
3. Washing the gum in an emulsion state is effective and efficient. In contrast, the wash of solid gum is extremely laborious if not impossible.
4. The toluene is easily recovered from the latex mass by steam distillation or vacuum evacuation.
5. The crude gum can be effectively purified by several means such as vacuum drying, steam distillation and solvent extraction.
Accordingly, it is one of the principal objects and advantages of this invention to provide a method of making a chewing gum base product maintaining all reactions in solution or emulsion form and resulting in easy materials handling and purification of the final product.
The present invention comprises a process of making a hydroxypropyl starch acetate which is suitable for use as a chewing gum base. The invention further comprises the processes hereinafter described and claimed.
The drawing is a schematic flow diagram of the process of this invention.